Transducers functioning at acoustic wavelengths are finding application in a variety of disparate technologies. Moreover, in many cases there is a need for comparatively small devices. These so-called miniaturized acoustic transducers generally utilize one of either a piezoelectric or a capacitive transduction mechanism. Transducers with capacitive transduction mechanisms sense a change in capacitance due to movement of one plate of a capacitor induced by a mechanical perturbation (acoustic wave). Transducers with piezoelectric transduction mechanisms sense a change in voltage due to oscillations induced by the acoustic wave.
Known piezoelectric-based transducers have clear benefits, but suffer certain drawbacks. For instance, bulk piezoelectric devices typically operate at comparatively high voltages (on the order of 102 V) to transmit an appreciable acoustic output. By contrast, some FBAR acoustic transducers are designed to operate at voltages one order of magnitude lower than bulk devices (e.g., 5V). As will be appreciated, and especially in applications requiring smaller transducers, the large driving voltages are not desirable. Rather, miniaturized transducers that are readily adapted to integration with otherwise low-voltage components are desired.
While known FBAR transducers show promise in many applications, parasitic elements can impact their performance. For instance, in receive mode, the transducer and receive electronics can be modeled as a voltage divider circuit. As a result, the signal to the amplifier at the receiver can be unacceptably small, thereby significantly impacting the performance of the transducer.
What is needed, therefore, is a transducer device that addresses at least the shortcomings of known devices.